1. Field of the Invention
The present invention relates to a flexible distribution sheet which is applied to connection in the interior of an electronic device or between such devices, and more particularly, it relates to a flexible distribution sheet having a structure for suppressing occurrence of an electromagnetic fault.
2. Description of the Background Art
In general, a flexible distribution sheet is widely employed in an electronic device such as an office automation product, to serve as a distribution interface in the interior of the device or between such devices. FIGS. 9A and 9B are a plan view and a sectional view showing an example of such a conventional Flexible distribution sheet 1. The flexible distribution sheet 1 is provided with a long sheet 2 having flexibility, which is made of synthetic resin, for example. A plurality of long conductors 3a to 3d are arranged on an upper surface of the sheet 2 in parallel with each other at prescribed intervals, to extend entirely along the longitudinal direction of the sheet 2. The plurality of conductors 3a to 3d are made of a metal material such as silver or copper, which is excellent in conductivity. The conductors 3a to 3d are generally formed by sticking metal foil onto the upper surface of the sheet 2 and thereafter etching the same, or providing such conductors 3a to 3d on one surface of the sheet 2 by plating.
The conductors 3a to 3d are covered with a cover film 4 of insulating resin, except both ends and portions which are around the same. The cover film 4 is formed by covering the conductors 3a to 3d with insulating resin, or sticking a film of insulating resin onto the conductors 3a to 3d.
The flexible distribution sheet 1 has sufficient flexibility as a whole, whereby it is possible to reliably electrically connect portions to be connected with each other with the flexible distribution sheet 1, even if an obstacle is present in a minute portion of the device or between the devices.
When an electric signal such as a digital signal having frequency components of a wide range is fed in the flexible distribution sheet 1 to cause impedance mismatching on ends of the conductors 3a to 3d, standing waves are generated in the conductors 3a to 3d due to resonance by reflection. Such generation of standing waves leads to increase in radiation efficiency for electromagnetic waves in a frequency band around the standing waves. Consequently, higher harmonic wave components and the like are radiated to the exterior, to cause an electromagnetic fault in an electronic device or a cable provided around the flexible distribution sheet 1.
In general, therefore, a filter element is connected to each end of the flexible distribution sheet 1 in order to remove EMI (electron magnetic interference) noise, thereby preventing the aforementioned electromagnetic fault resulting from impedance mismatching. Such a noise filter has a structure such as an L-type, .pi.-type or T-type structure, which is formed by a capacitor and an inductor.
However, such a noise filter is merely adapted to remove the aforementioned EMI noise, with no contribution to an operation of the electronic device in which the same is assembled. Therefore, omission of such a noise filter is awaited for the purpose of miniaturizing the electronic device.